Method of plating nonconductor product

ABSTRACT

A nonconductor product is soaked in a solution suspending a semiconducting powder and is subjected to light irradiation in the solution so that polar group is formed on the surface of the nonconductor product, and then electroless plating is performed on the surface on which the polar group is formed. A resin product is subjected to electroless plating after ultraviolet treatment in which ultraviolet rays are irradiated through water or a solution is performed. Further, electroless plating or electroplating with a different or the same kind of metal is performed on the electroless-plated layer formed by electroless plating. With the method like this, the plated nonconductor product which does not cause problems such as environmental pollution and waste liquid treatment, and whose surface and plated coating is firmly adhered to each other, and, when a resin product is used as an object to be plated, deformation by heat of the resin product can be prevented, and moreover, the adherent strength of the plated coating can be improved.

FIELD OF THE INVENTION

The present invention relates to, in performing electroless plating onthe surface of a nonconductor product, a method of plating anonconductor product in which the product is pretreated and then treatedwith electroless plating, to a method of plating a nonconductor productin which electroless plating or electroplating is performed on theformed electroless plated layer, and to the nonconductor product platedwith these methods, with the plated nonconductor product beingadvantageously used for wheeled vehicles, information equipment, officeequipment, ornamental articles and the like.

BACKGROUND OF THE INVENTION

As a method of giving conductivity or metallic luster to a nonconductorproduct, there have been known a method of depositing metal to thenonconductor product in vacuum, a method of sputtering metal to thesame, a method of electroless plating on the same, and the like.Electroless plating is a method of chemically reducing and depositingmetal ions in a solution to make a metallic coating form on the surfaceof the material, even on the surface of an insulating material includinga resin and the like, which is different from electroplating in which ametal coating is electrolytically deposited by electricity.

Plated coatings formed by electroless plating, however, have the problemof not having sufficient adherent strength to the surface of thematerial. Therefore, when electroless plating is carried out, there havebeen known, as pretreatment thereof, methods of electroless plating suchas surface roughening in which the surface of a nonconductor product ischemically etched, with the addition of a polar group and treatment by acatalyst. Treatments of surface roughening and addition of the polargroup are mainly carried out with chemicals including chromic acid,permanganic acid, and sulfuric acid and the like. These chemicals have aproblem that they become a cause of environmental pollution and cost ahuge sum for treatment of the waste liquid. Further, surface rougheningand addition of the polar group are performed with a treatment by plasmaor corona discharge and the like. As the treatment by plasma or coronadischarge and the like should be generally done in a vacuum, therebecomes a problem in the productivity, and the development ofalternative treatment methods have been sought.

As a method of electroless plating on a resin product, Japan PatentLaid-Open Publication No. 1-092377 discloses a method in which a resinmolding is pretreated with ozone gas and is then treated withelectroless plating. According to the same publication, unsaturatedbonds on the surface of resin are cleaved by ozone gas to turn into lowmolecules, molecules with different compositions coexist on the surface,depriving smoothness from the surface to make it rough. The samepublication thus describes that the coating formed with electrolessplating penetrates well into the rough surface without being strippedoff easily.

In the method described above, adherent strength of the plated coatingis improved by roughening the resin surface, namely, by a so-calledanchoring effect. In the method of roughening the surface, however, thesmoothness thereof is lowered, so that, in order to obtain a surfacewith a metallic luster having a high-grade design performance, theplated coating needs to be thickened, which causes a disadvantage of anincreased number of man-hours.

Japan Patent Laid-Open Publication No. 8-253869 thus discloses a methodin which electroless plating is performed after ultraviolet rays areirradiated on a resin surface. With this method, the resin surface isactivated by ultraviolet radiation, and active groups on the activatedresin surface chemically bond with the molecules of metal which is thematerial for plating, making the adherent strength of the plated coatingimproved. Further, as the resin surface is not easily roughened, ametallic luster having a high-grade design performance can be obtained.

Japan Patent Laid-Open Publication No. 10-88361 further discloses amethod in which electroless plating is performed in such a way that,after ultraviolet rays are irradiated on a resin molding as apretreatment for electroless plating, the resin molding is contactedwith an alkali solution containing a nonionic surfactant having apolyoxyethylene linkage. Also with this method, as the resin surface isactivated by ultraviolet radiation and is not easily roughened, ametallic luster having high-grade design performance can be obtained.

In the meantime, a light source for ultraviolet radiation generates notonly ultraviolet rays but also infrared and far-infrared rays. Inaddition, in order to activate a resin surface, a large quantity ofenergy as well as radiation for a relatively long period of time isnecessary. A large quantity of heat is thus applied to the resin moldingfrom the light source at the time of ultraviolet radiation, which maydisadvantageously cause deformation of the resin molding by heat in sometypes of resin. Further, in some forms of the resin molding, a shadowedsection from ultraviolet radiation is made due to being situated in adead area of the light axis, which may make it difficult to irradiateultraviolet rays onto the shadowed section.

According to a study made by the present inventors, on the other hand,when the dosage of ultraviolet irradiation is too much, it is evidentlyobserved that the adherent strength of the plated coating, on thecontrary, lowers.

As a method of giving a metallic luster to a nonconductor product, themethods as described above may satisfy the need in some cases, butaccording to the usage of the nonconductor product, further electrolessplating or electroplating thereon may be required when a higherendurance and fanciness is required.

The present invention is made in view of the situation described above,and the object of the present invention is; firstly, to provide a methodof plating a nonconductor product in which, when the nonconductorproduct is pretreated by electroless plating, the plated nonconductorproduct with the plated layer and the surface of the nonconductorproduct being tightly adhered to each other can be obtained withoutcausing any problems such as environmental pollution and treatment ofthe waste liquid; secondly, to provide a method of plating anonconductor product in which, when a resin product is pretreated as anobject to be plated by electroless plating using ultraviolet radiation,deformation of the resin product by heat can be prevented and theadherent strength of the plated coating can be further improved;thirdly, to provide a method of plating a nonconductor product in whicha plated coating with a higher endurance and fanciness can be formedthereon; and fourthly, to provide the plated nonconductor productobtained by these methods.

DISCLOSURE OF THE INVENTION

The invention to solve the first problem described above is a method ofplating a nonconductor product characterized in that the nonconductorproduct is soaked in a solution suspending a semiconducting powder, thepolar group is formed on the surface of the nonconductor product bylight irradiation in the solution, and electroless plating is performedon the surface on which the polar group is formed.

In this invention, as the preferred semiconductor, one selected from thegroup consisting of titanium dioxide, zinc oxide, cadmium sulfide,gallium phosphide, silicon carbide, indium oxide, and vanadium oxide isexemplified, and the particle diameter of the semiconducting powder ispreferably in the range from 0.1 to 1,000 μm. Further, in thisinvention, the solution suspending the semiconducting powder ispreferably an aqueous or nonaqueous solution, the irradiated light ispreferably ultraviolet light or visible light, and the polar group ispreferably formed directly on the surface of the nonconductor product.Moreover, in this invention, as preferred material of the nonconductorproduct, one selected from the group consisting of a resin, rubber,ceramics and glass is exemplified, and if the nonconductor productcomprises a resin, the resin may contain a semiconducting powder.

The invention to solve the second problem described above is a method ofplating a nonconductor product characterized in that, after a resinproduct is treated with ultraviolet radiation through water or asolution, the resin product is subjected to electroless plating.

In this invention, ultraviolet treatment is preferably performed in sucha way that the resin material is soaked in water or a solution whilebubbling of air is carried out therein. The solution used is preferablya solution containing a dissolved oxidizing agent or alkali material.Further, it is preferable to, after the ultraviolet treatment as well asbefore the electroless plating, give the resin material a secondtreatment in which at least one of the anionic surfactant and nonionicsurfactant as well as a solution containing an alkali ingredient(s) arecontacted with the resin material.

The invention to solve the above third problem described above is, amethod of plating a nonconductor product in which electroplating with adifferent or the same kind of metal is further performed on theelectroless-plated layer formed by electroless plating in the inventiondescribed above.

In the invention described above, as the metal for electroless plating,a metal selected from the group consisting of nickel, copper, gold,silver, and a metallic compound thereof is exemplified.

The invention to solve the fourth problem described above is the platednonconductor product obtained with the methods described above.

BRIEF DESCRIPTION OF THE DRAWING

FIG. 1 is an explanatory view showing the state where ultraviolettreatment is performed according to one embodiment of the presentinvention, and in the FIGURE, the reference numeral 1 indicates a resinboard, 2 a transparent silicic vessel, 3 pure water, and 4 ahigh-pressure mercury lamp.

PREFERRED EMBODIMENTS OF THE INVENTION

The present invention is described below in detail.

(1) The method of plating a nonconductor product to solve the firstproblem is that the nonconductor product is soaked in a solutionsuspending a semiconducting powder, the polar group is formed on thesurface of the nonconductor product by light irradiation in thesolution, the surface on which the polar group is formed is contactedwith a catalyst(s) and activated according to the common procedure, andthen electroless plating is performed thereon.

The semiconducting powder used for this invention is semiconductingpowder having the character of a photoelectrode. Examples of thesemiconductor are preferably titanium dioxide, zinc oxide, cadmiumsulfide, gallium phosphide, silicon carbide, indium oxide, and vanadiumoxide and the like. Anatase-type titanium dioxide is more preferable.

A semiconducting powder in any form can be used. The particle diameterof the powder is preferably in the range from 0.1 to 1,000 μm, morepreferably from 0.1 to 10 μm, and further preferably from 0.1 to 5 μm.If the anatase-type titanium dioxide is used in particular, the particlediameter of the powder is preferably in the range from 0.1 to 3 μm.

In this method, the nonconductor product is soaked in a solutionsuspending a semiconducting powder, and it is preferable that thesolution is agitated and the semiconducting powder is uniformlydispersed in the solution.

The solution used for the present invention preferably contains thesemiconducting powder in an amount of 0.01 to 99% by weight. If thesemiconducting powder content is less than 0.01% by weight, the polargroup may not be formed sufficiently on the surface of the nonconductorproduct in the treatment by light irradiation. On the other hand, if thesemiconducting powder content is more than 99% by weight, the polargroup may not be dispersed uniformly. The semiconducting powder contentis more preferably in the range of from 0.01 to 20% by weight.

In addition, the semiconducting powder can carry a metal, includingplatinum and palladium and the like, in an amount of from 0.01 to 10% byweight to the gross weight of the semiconducting powder. If thesemiconducting powder carrying a metal, including platinum and palladiumand the like, is used, the polar group is added to the surface of thenonconductor product more effectively.

The solution to suspend a semiconducting powder used for the presentinvention is an aqueous or nonaqueous liquid, and as the aqueoussolution to suspend a semiconducting powder, water, sulfuric acidsolution, nitric acid solution and the like is exemplified with a liquidcontaining a sulfonic group, nitro group and the like being preferable.The concentration of a solution with sulfuric acid or nitric acid ispreferably in the range from 0.01 to 99% by weight, and more preferablyin the range from 0.1 to 20% by weight. Thus, for example, in nitricacid is contained in the solution, addition of the nitro group changesthe state of the resin surface from being stable to unstable, which ispreferable because the plated layer to be formed is firmly adhered tothe surface. As the nonaqueous liquid, alcohols and ethers areexemplified.

The solution to suspend a semiconducting powder can be added with aphotosensitizing agent in the range from 1 to 50% by weight to the grossweight of the solution. Adding a photosensitizing agent effectively addsthe polar group to the surface of the nonconductor product. As thephotosensitizing agent, each ion of palladium, nickel, copper, iron,gold, platinum and the like is exemplified, with an iron ion beingpreferable.

The irradiated light is preferably ultraviolet or visible light, andultraviolet radiation is preferable in particular. Examples of the lightsource are a low-pressure mercury lamp, high-pressure mercury lamp,xenon lamp, tungsten lamp, halogen lamp, various kinds of laserincluding excimer laser, barrier discharge lamp, dielectric barrierdischarge lamp, microwave electrodeless discharge lamp, overdischargelamp, and the like. If the nonconductor product is made of, for examplea resin, ultraviolet light with which the bonds on the resin surface iscleaved leading to a stable plated layer is preferable. Ultravioletlight is also called ultraviolet rays, referring to light with awavelength in the range from 400 to 4 nm. Visible light, in themeantime, is also called visible rays, referring to light with awavelength in the range from 400 to 750 nm.

With this method, the polar group is formed by light irradiation on thesurface of the nonconductor product. The period of time for lightirradiation is selected properly depending on the type of a nonconductorproduct or semiconducting powder to be used, and the light irradiationtime is preferably in the range from 1 to 180 minutes. At this time thesurface of the nonconductor product is oxidized by thephoto-electrochemical reaction of the semiconducting powder, and afunctional group in the suspended solution is added to the surface ofthe nonconductor product where the polar group is formed tosignificantly increase the chemical bond, making the adherence of thesurface to the plated coating firm. In particular, irradiation of amercury lamp for 5 to 30 minutes is preferable. Upon irradiating thelight, it is more preferable that supersonic vibration is carried out atintervals of every certain period of time in order to removesemiconducting powder absorbed on the surface of a nonconductor product.

As the polar group formed on the surface of the nonconductor product,for example, a carbonyl group (C═O), carboxyl group (COOH) and the likeare exemplified. If, for example, anatase-type titanium dioxide is usedas the semiconducting powder, the reaction proceeds from hydroxideradicals generated by the chemical reaction with water, which forms thecarbonyl group having a hydrophilicity on the surface of thenonconductor product to improve the wettability on the surface of thesame. Polar groups may be formed on any layer formed on the surface ofthe nonconductor product according to the common procedure, while thepolar group is preferably formed directly on the surface of thenonconductor product.

In this invention, the nonconductor product refers to a molding made ofa material having a large electrical resistance and, for practical use,of that used as an electrical insulating material, so that examples ofthe material are a resin, rubber, ceramic, glass and the like. When thematerial is a resin, the type of the resin to be used is notspecifically limited, and, for example, anacrylonitrile-butadiene-styrene resin (ABS resin), polyimide resin,epoxy resin, polyethylene terephthalate resin (PET resin), andpolystyrene resin (PS resin) is exemplified. The form of the resin isnot in any way limited but it may have the form of a plate, sphere,particle, and the like.

In this invention, when a resin product is used as the nonconductorproduct, the semiconducting powder described above may be contained inthe resin product to be used, and the preferable semiconducting powderis anatase-type titanium dioxide. The content of semiconducting powderin the resin on its surface is preferably less than 80% by weight.

Electroless plating is then performed in the same way as theconventional treatment of electroless plating on the surface of thenonconductor product on which the polar group is formed.

(2) The method of plating a nonconductor product to solve the secondproblem is that the subject to be plated is a resin product, andelectroless plating is performed onto the resin product after the resinproduct is treated with ultraviolet radiation through water or asolution. A resin product refers to a molding made of a resin.

When the resin product is irradiated by ultraviolet radiation throughwater or a solution, the resin product is cooled due to the absorptionof heat rays by the water or solution first or the evaporation of water,which can prevent the resin product from being overheated, inhibitingdeformation thereof by heat. Further, even when the dosage of theultraviolet irradiation increases, there does not occur such a problemas a decrease in adherent strength of the plated coating. It iscontemplated that this is because the surface of the resin is somewhatoxidized and activated by the hydroxyl groups of the water.

When the resin product is irradiated by ultraviolet radiation throughwater or a solution, it is also possible that at least the surface ofthe resin product to be irradiated in the state of being wet with wateror a solution may be subjected to ultraviolet irradiation, but it ispreferable that the resin product in the state of being soaked in wateror a solution is subjected to ultraviolet irradiation from outside thevessel. With this method, a sufficient volume of water is secured, whichcan further inhibit the temperature of the resin product from rising andprevent the thermo-deformation thereof.

The resin used herein is one which generates active groups on itssurface by ultraviolet irradiation, and the resin of this kind isillustrated by a polyethylene resin, polypropylene resin, ABS resin,acrylonitrile-styrene copolymer (AS resin), PS resin, acrylonitrileresin (AN resin), epoxy resin, polymethylmethacrylate resin (PMMAresin), polyacetal resin (PA resin), polyester resin, polyoxymethyleneresin (POM resin), polycarbonate (PC resin), PET resin, polybutyleneterephthalate resin (PBT resin), polyimide resin, and polyphenyl sulfideresin and the like.

As ultraviolet rays to be irradiated, any electromagnetic waves withinthe ultraviolet region can be used, while in consideration of activatingthe surface of the resin product, electromagnetic waves with awavelength in the range from 400 nm to 50 nm is preferably used, morepreferably, less than 310 nm, further preferable less than 260 nm, andfurther preferably in the range from about 150 to about 200 nm. Thedosage of ultraviolet irradiation is preferably more than 50 mJ/cm².

The light source which can irradiate such ultraviolet rays as describedabove can be a low-pressure mercury lamp, high-pressure mercury lamp,excimer laser, barrier discharge lamp, dielectric barrier dischargelamp, microwave electrodeless discharge lamp, overdischarge lamp, andthe like. When the resin product is soaked in water or a solution andirradiated by ultraviolet rays, the use of a vessel into whichultraviolet rays can easily penetrate is preferable, and the use of atransparent silicic vessel is especially preferable.

As the solution described above, it is preferable to use a solutioncontaining a dissolved oxidizing agent or alkali material. When asolution containing a dissolved oxidizing agent or alkali material isused, activation on the resin surface by ultraviolet irradiation isexpedited so that the adherent strength of the plated coating isimproved, even when the dosage of ultraviolet irradiation is decreased.The heat quantity received by the resin product can thus be reduced,enabling the further prevention of the resin product from deforming byheat. In the meantime, in order to reduce the dosage of ultravioletirradiation, either weakening the light from the light source orshortening the time of irradiation is available.

As the oxidizing agent, sodium perchlorate, potassium perchlorate,sodium peroxide, potassium peroxide, hydrogen peroxide and the like areexemplified. As the alkali material, sodium hydroxide, potassiumhydroxide and the like are preferable, and ammonia can also be used insome cases. The concentration of the oxidizing agent or alkali materialin a solution is not specifically limited, but it is preferable todetermine the concentration by trial and error in accordance with thetype of oxidizing agent or alkali material as well as of the resinproduct.

Further, when the resin material is soaked in water or a solution to beirradiated by ultraviolet rays, the irradiation is preferably carriedout while bubbling air. By doing so, ultraviolet rays are diffuselyreflected by the bubbles so that they can be irradiated even onto ashadowed section situated in a dead area of the light axis of the resinproduct, enabling the formation of a plated coating having high adherentstrength also in the shadowed section. The bubbles may be of atmosphereair and the use of an oxidizing gas such as ozone is also preferable.

The resin product after the ultraviolet treatment as described above canbe subjected to electroless plating without any pretreatment, but ispreferably subjected to a second treatment in which at least one of theanionic surfactant and nonionic surfactant, and a solution containing analkali ingredient(s) are contacted with the resin product.

In this process of the second treatment, it is contemplated that thehydrophobic group of the surfactant after the ultraviolet treatmentabsorbs the active group turning up onto the surface of the resinproduct. The alkali ingredient has a function of dissolving the surfaceof the resin product on the molecular level, which enables an embrittledlayer on the surface of the resin product to be removed to turn up moreactive groups. Thus the surfactant also absorbs another active groupturning up onto the surface of the resin product by removing theembrittled layer.

As the surfactant, the one whose hydrophobic group easily absorbs atleast one of the functional group consisting of C═O and C—OH is used sothat at least one of the anionic surfactant or nonionic surfactant isemployed. If a cationic surfactant and neutral surfactant is used, aplated coating may not be formed or it may be difficult to produce adesired effect. As the anionic surfactant, sodium lauryl sulfate,potassium lauryl sulfate, sodium stearyl sulfate, potassium stearylsulfate, and the like is exemplified. As the nonionic surfactant,polyoxyethylene dodecyl ether, polyethyleneglycol dodecyl ether, and thelike is exemplified.

As the alkali ingredient, the ingredient which can dissolve the surfaceof a resin product on the molecular level to remove an embrittled layercan be used, and sodium hydroxide, potassium hydroxide, lithiumhydroxide, and the like is employed.

As a solvent of the solution containing the surfactant and alkaliingredient, a polar solvent is preferably used, so that water can betypically employed, while alcohol solvents or a water-alcohol mixedsolvent can be used if necessary. In order to contact a solution with aresin product, measures including soaking the resin product in thesolution, applying the solution on the surface of the resin product, andspraying the solution onto the surface of the resin product can becarried out.

The concentration of the surfactant in a solution is preferably in therange from 0.01 to 10 g/L. If the concentration of the surfactant in asolution is less than 0.01 g/L, the adherence of the plated coating islowered, while if the concentration of the surfactant in a solution ismore than 10 g/L, the adherence of the plated coating is also loweredbecause the surfactant turns to be in the state of association with anexcessive surfactant remaining as impurities. In this case, theexcessive surfactant can be removed by washing the resin product withwater after the treatment.

The concentration of the alkali ingredient in a solution preferably hasa pH of 12 or more. Although some effects can be obtained with a pH lessthan 12, the active group turning up onto the surface becomes less andthe adherence of the catalytic metal decreases, making it difficult toform a plated coating.

The contact time of the solution with the resin product in the secondtreatment is not specifically limited, but it is preferably more thanone minute at room temperature. If the contact time is too short, theamount of the surfactant absorbing the active group may be insufficientto lower the adherence of the plated coating. If the contact time is toolong, however, even the layer where the active group turns up may bedissolved to make electroless plating difficult so that a contact timein the range from about 1 to about 5 minutes is enough. Further, ahigher temperature is preferable in the second treatment. While thehigher the temperature is, the shorter the contact time becomes, atemperature in the range from room temperature to about 60° C. isenough.

In the second treatment, the surfactant may be absorbed after treatmentwith a solution containing only an alkali ingredient, but the treatmentis preferably made in the state where at least one of the anionicsurfactant and the nonionic surfactant, and the alkali ingredientcoexist because an embrittled layer may be formed again before theabsorption of the surfactant.

After the second treatment, a process to wash with water and remove thealkali ingredient may be carried out. It is understood that, as thesurfactant firmly absorbs the active group, it is not removed by washingwith water and the like but keeps the state of absorption. Thus theresin product treated as described does not lose the effect even if acertain period of time passes before the electroless plating treatment.

In the electroless plating treatment, the resin product absorbing thesurfactant is first contacted with a catalyst. It is contemplated thatthe catalyst is absorbed by the hydrophilic group of the surfactantabsorbing the active group and by performing electroless plating on theresin product having sufficiently absorbed the catalyst, it isconsidered that the surfactant is freed from the functional group whilethe functional group is bonded to the plating metal so that a platedcoating having excellent adherent strength can be formed.

As the catalyst, one used for conventional electroless plating includingPd²⁺ may be employed. In order to make the catalyst absorb onto thesurface of the resin product, a solution of the catalyst may be simplycontacted with the surface of the resin product, which can be carriedout in the same way as the contact thereof with a solution describedabove. Conditions such as the contact time and temperature are the sameas those in the conventional procedure. Conditions of electrolessplating, the type of metal to be deposited and the like are not limitedand are also the same as those in the conventional procedure.

(3) If electroless plating or electroplating according to the commonprocedure is further performed on the electroless plating layer formedwith the method of plating a nonconductor product described about in (1)and (2), a plated layer having further excellent endurance can beobtained, so that it is preferable that electroless plating orelectroplating is further performed on the electroless plated layer.

In the method (1) described above of plating a nonconductor product, themethod (2) of plating a nonconductor product, and the method (3) ofplating a nonconductor product, as electroless plating metal, forexample, a metal selected from the group consisting of nickel, copper,gold, silver, and a metallic compound thereof is exemplified, and nickelor copper is preferable. As an electroplating metal, copper, nickel,chromium, tin-nickel, gold, and the like is exemplified.

(4) Of the plated nonconductor products obtained with the methods ofplating a nonconductor product as described in (1) to (3), those in theform of a board are plated to be used as print-wiring boards and thelike, those in the form of a particle are plated to be used asconductive particles, and those dispersed in vehicles are plated to beused as conductive adhesive agents, paint, and the like. If the platednonconductor product is used as print-wiring boards, it may have amultilayered structure alternately laminating a plated layer and aninsulated layer on a basal board. Further, the plated nonconductorproduct has a metallic luster and the plated coating thereof firmlyadheres onto the material surface so that such plated nonconductorproduct can be used for wheeled vehicles, information equipment, officeequipment, ornamental articles and the like.

EXAMPLES

The present invention is specifically described below with reference tothe examples. The present invention, however, is not limited to theseexamples.

Example 1

As the nonconductor product, a resin basal board (25×100 mm) formed ofan ABS resin was employed. An anatase-type titanium dioxide,semiconducting powder, having the particle diameter of 1.0 μm was putinto a solution with a nitric acid content of 5% by weight to prepare asolution with a powder content of 10% by weight and was agitated with amagnetic stirrer to obtain a solution with the powder uniformlydispersed and suspended therein. The ABS resin basal board was soaked inthe solution and was irradiated with ultraviolet rays having thewavelength of 245 nm from the light source of a mercury lamp for 10minutes to form the carbonyl groups on the surface of the ABS resinboard. The surface of the ABS resin board formed with the carbonylgroups was activated according to the common procedure and was subjectedto electroless nickel plating. Then the surface of the ABS resin boardwas further subjected to electric copper plating. The adherent forcebetween the plated layer obtained and the surface of the ABS resin boardwas 1.0 kgf/cm or more. Further, the backside of the basal board whichwas not directly irradiated with ultraviolet rays was, like in thesection subjected to direct irradiation, electroless nickel-platedduring the electroless plating, and was electrolytically copper-platedduring the electroplating, with the adherent force between the platedlayer obtained and the surface of the ABS resin basal board being 1.0kgf/cm or more.

In order to evaluate the adherent force, after the electroplating, ventswere cut at 1 cm intervals reaching from the plated layer down to theresin basal board and the adherent strength of the plated coating wasmeasured with a tensile tester.

Example 2

As the nonconductor product, a resin basal board (25×100 mm) formed of apolyimide resin was used, except that the same procedure as Example 1was employed to form the carbonyl groups on the surface of the polyimideresin board, then to perform electroless nickel plating according to thecommon procedure, and to carry out electrolytic copper plating. Theadherent force between the obtained plating layer and the surface of theresin board was 1.0 kgf/cm or more. Further, the backside of the basalboard which was not directly irradiated with ultraviolet rays was, likein the section, subjected to direct irradiation, electrolessnickel-plated during the electroless plating, and was electrolyticcopper-plated during the electroplating, with the adherent force betweenthe plated layer obtained and the surface of the resin basal board being1.0 kgf/cm or more.

Example 3

As the nonconductor product, a resin basal board (25×100 mm) formed ofan epoxy resin was employed and a solution with nitric acid content of10% by weight was used, except that the same procedure as Example 1 wasemployed to form the carbonyl groups on the surface of the epoxy resinboard, then to perform electroless nickel plating according to thecommon procedure, and to carry out electrolytic copper plating. Theadherent force between the plated layer obtained and the surface of theABS resin board was 1.0 kgf/cm or more. Further, a through hole with ahole diameter of 1 mm was opened onto the epoxy resin board to similarlyperform electroless nickel plating and then electrolytic copper plating.The plated epoxy resin board obtained was subjected to a pulling-outtest of the through hole according to JIS C5012 8.3, with the result ofthe test being 8 kg or more.

Example 4

As the nonconductor product, a flexible resin basal board (25×100 mm)formed with polyimide resin was used, except that the same procedure asExample 1 was employed to form the carbonyl groups on the surface of thepolyimide resin board, then to perform electroless copper platingaccording to the common procedure. Then electrolytic copper plating wascarried out on the layer plated with electroless copper plating. Theadherent force between the plated layer obtained and the surface of theresin board was 0.7 kgf/cm or more. Further, the backside of the basalboard, which was not directly irradiated with ultraviolet rays, was,like in the section subjected to direct irradiation, electrolesscopper-plated during the electroless plating, and was electrolyticcopper-plated during the electroplating, with the adherent force betweenthe plated layer obtained and the surface of the resin basal board being0.7 kgf/cm or more.

Example 5

As the nonconductor product, a flexible resin basal board (25×100 mm)formed with PET (polyethylene terephthalate) resin was used, except thatthe same procedure as Example 1 was employed to form the carbonyl groupson the surface of the PET resin board and to perform electroless copperplating according to the common procedure. Then electrolytic copperplating was carried out on the layer plated with the electroless copperplating. The adherent force between the plated layer obtained and thesurface of the resin board was 0.9 kgf/cm or more. Further, the backsideof the basal board which was not directly irradiated with ultravioletrays was, like in the section subjected to direct irradiation,electroless copper-plated during the electroless plating, and waselectrolytically copper-plated during the electroplating, with theadherent force between the plated layer obtained and the surface of theresin basal board being 0.9 kgf/cm or more.

Example 6

As the nonconductor product, the anatase-type titanium dioxide havingthe particle diameter of 1.0 μm was uniformly mixed into an epoxy resinin liquid form to prepare a mixture with the titanium dioxide content of50% by weight and the mixture was applied to have a thickness or 50 μmon an epoxy basal board (25×100 mm), and a solution with a nitric acidcontent of 10% by weight was used, except that the same procedure asExample 1 was employed to form carbonyl groups on the surface of theepoxy resin board, then to perform electroless nickel plating accordingto the common procedure, and to carry out electrolytic copper plating.The adherent force between the plated layer obtained and the surface ofthe resin board was 1.0 kgf/cm or more.

Example 7

As the nonconductor product, spherical particles having an averageparticle diameter of 5 μm formed of a polystyrene resin was employed anda solution with a nitric acid content of 10% by weight was used, exceptthat the same procedure as Example 1 was employed to form the carbonylgroups on the surface of the polystyrene resin-made spherical particles.Then, the surface of the polystyrene resin-made particles formed withcarbonyl groups were activated according to the common procedure to besubjected to electroless nickel plating. Then electrolytic copperplating was carried out on the surface of the particles, with which theadherent strength of the plated layer obtained was excellent and capableof being used as conductive particles.

Example 8

As the nonconductor product, a resin board 1 defatted and made of an ABSresin was used, and as shown in FIG. 1, the board 1 was soaked in purewater 3 filled in a transparent silicic vessel 2 to be irradiated withultraviolet rays from outside the vessel 2 using a 1 kw high-pressuremercury lamb 4. Ultraviolet rays were irradiated for 5 types of periodsof time as a reference, namely, 1, 3, 5, 7, and 10 minutes to make eachresin board 1 treated with ultraviolet rays.

Next a solution dissolving and mixing 50 g/L NaOH and 1 g/L sodiumlauryl sulfate was heated to 60° C. to soak therein each of theultraviolet-treated resin boards for 2 minutes and to absorb an anionicsurfactant (sodium lauryl sulfate).

Each resin board absorbing the surfactant was taken out from thesolution to be washed with water and dried, was soaked for 3 minutes ina catalytic solution in which a palladium chloride content of 0.1% byweight as well as a tin chloride content of 5% by weight was dissolvedin a 3N hydrochloric acid solution to be heated to 50° C., and wasfurther soaked for 3 minute in a 1N hydrochloric acid solution toactivate the palladium. Thereby, the resin board absorbing catalyst foruse in plating was obtained.

Each resin board used in plating was then soaked in a nickel chemicalplating bath kept warm at a temperature of 40° C. to deposit a nickelplated coating for 10 minutes. The nickel plated coating deposited had athickness of 0.5 μm. Each resin board was then soaked in a coppersulfate Cu electroplating bath to deposit a copper plating of 100 μm onthe surface of the nickel plated coating.

A depth of cut was inserted on the plated coating of each obtained resinboard at 1 cm intervals reaching down to the resin basal board and theadherent strength of the plated coating was measured with a tensiletester. Visual evaluation was also made concerning the externalappearance of each resin board. The result is shown in Table 1.

Example 9

A solution with sodium perchlorate having the concentration of 5% byweight was used instead of pure water, except that the same procedure asExample 8 was employed to perform ultraviolet treatment for 5 types ofperiods of time as a reference. Each resin board was then subjected to aplated coating formation with the same procedure as Example 8, andsimilarly, the adherent strength thereof was measured and visualevaluation of the external appearance thereof was made. The result asshown in Table 1.

Example 10

A solution with sodium hydroxide having the concentration of 5% byweight was used instead of pure water, except that the same procedure asExample 8 was employed to perform ultraviolet treatment for 5 types ofperiods of time as a reference. Each resin board was then subjected to aplated coating formation with the same procedure as Example 8, andsimilarly, the adherent strength thereof was measured and visualevaluation of the external appearance thereof was made. The result isshown in Table 1.

Comparative Example 1

Except that ultraviolet rays were irradiated in the atmosphere, the sameprocedure as Example 8 was employed to perform ultraviolet treatment for5 types of periods of time as a reference. Each resin board was thensubjected to a plated coating formation with the same procedure asExample 8, and similarly, the adherent strength thereof was measured anda visual evaluation of the external appearance thereof was made. Theresult is shown in Table 1.

Evaluation

TABLE 1 Time of UV Adherence Appearance Condition of irradiationStrength of UV irradiation (min) (kgf/cm) resin board Example 8 In water1 not adhering not abnormal 3 not adhering not abnormal 5 0.5 notabnormal 7 1.0 not abnormal 10  1.2 not abnormal Example 9 In a solution1 0.6 not abnormal with sodium 3 1.2 not abnormal perchlorate 5 1.2 notabnormal 7 1.3 not abnormal 10  1.4 not abnormal Example 10 In asolution 1 not adhering not abnormal with sodium 3 0.6 not abnormalhydroxide 5 0.9 not abnormal 7 1.3 not abnormal 10  1.3 not abnormalComparative In the 1 not adhering not abnormal Example 1 atmosphere 3not adhering not abnormal 5 0.5 Curve 7 1.2 Curve 10  0.9 Curve

According to Table 1, Comparative Example 1 shows that the resin boardwas deformed by heating with ultraviolet irradiation for 5 minutes ormore, while each Example shows that deformation by heat was prevented,even with ultraviolet irradiation for 10 minutes. It is contemplatedthat this is due to the prevention of overheating of the resin boardwith water or the solution.

Each resin board treated in Example 9 and Example 10 showed a greatlyimproved adherent strength compared with those treated in Example 8. Itis thus obvious that the resin board is preferably treated withultraviolet irradiation in the solution with an oxidizing agent oralkali rather than in water.

If, for example, Example 9 and Example 8 are compared with each other,the resin board treated in a sodium perchlorate solution withultraviolet irradiation for 3 or 5 minutes had a similar adherentstrength to that treated in water with ultraviolet irradiation for 10minutes. Ultraviolet irradiation in a sodium perchlorate solution canthus shorten the irradiation time compared to the irradiation in water,which improves the productivity.

Moreover, in Example 1, the resin board treated with ultravioletirradiation for 10 minutes had a lower adherence strength compared tothat treated with ultraviolet irradiation for 7 minutes, while inExample 8, the resin board treated with ultraviolet irradiation for 10minutes had a further higher adherence strength compared to that treatedwith ultraviolet irradiation for 7 minutes. Namely, ultravioletirradiation in water can prevent the adherent strength fromdeteriorating from irradiation for a longer period of time.

Example 11

As the nonconductor product, a radiator grill molded from an ABS resinwas used. The radiator grill was soaked in pure water filled in atransparent silicic vessel having 20 air bubbling openings on its lowerpart, and was irradiated with ultraviolet rays for 15 minutes using thesame procedure as Example 8, while air was bubbling from the airbubbling openings. The radiator grill was then subjected to a platedcoating formation as in Example 8.

Example 12

As the nonconductor product, a radiator grill of the same kind as thatused in Example 11 was employed and air bubbling was not carried out,except that the same procedure as Example 11 was performed to irradiateultraviolet rays, and similarly the radiator grill was subjected to aplated coating formation.

Evaluation

In Example 11 and Example 12, deformation was not observed in eitherradiator grill. In Example 12, a plated coating was not formed on ashadowed section from ultraviolet radiation situated in a dead area ofthe light axis. This is because the nickel plated coating did not adhere(stripped off). In Example 11, on the other hand, a plated coating wasformed all over the radiator grill with a high adherence strength. It isobvious that this results from the effect of air bubbling.

Industrial Availability

With the method of plating a nonconductor product according to thepresent invention, a plated layer firmly adhered to the surface of thenonconductor product can be formed without laying a burden on theenvironment. Further, when the treatment for surface roughening andaddition of the polar group is made before electroless plating, it isnot necessary to use chemicals such as chromic anhydride and permanganicacid, which does not cause the problem of environmental pollution, andenables the treatment of waste liquids at a low disposal cost, and iseconomically advantageous as well.

With the method of plating a nonconductor product using a resin productas an object to be plated, deformation by heat of the resin product canbe certainly prevented. Further, if a solution with a reducing agent(s)or alkali is used during ultraviolet irradiation, the adherent strengthof a plated coating can be improved, so that it is possible to shortenthe irradiation time, which increases the productivity. In addition, ifbubbling is carried out in ultraviolet irradiation, a plated coatinghaving an excellent adherent strength is formed also on a shadowedsection from ultraviolet radiation situated in a dead area of the lightaxis.

Further, with the method of plating a nonconductor product according tothe present invention, a plated nonconductor product having an enduranceand fanciness can be obtained. Depending on the form of the nonconductorproduct to be used, that in the form of a board is plated to be used asa print-wiring board and the like, that in the form of a particle isplated to be used as a conductive particle, and that dispersed invehicles is plated to be used as a conductive adhesive agent, paint, andthe like. The plated nonconductor product has a metallic luster and theplated coating is firmly adhered to the material surface, which enablesthe plated nonconductor product to be used for, for example, wheeledvehicles, information equipment, office equipment, ornamental articlesand the like, and is extremely useful for functional plated products andornamental plated products.

1. A method of plating a nonconductor product, comprising the steps ofsoaking the nonconductor product in a solution suspending asemiconducting powder; forming a polar group on a surface of thenonconductor product by light irradiation in the solution; andperforming electroless plating on the surface on which said polar groupis formed.
 2. The method of plating a nonconductor product according toclaim 1, wherein the powder is selected from the group consisting oftitanium dioxide, zinc oxide, cadmium sulfide, gallium phosphide,silicon carbide, indium oxide, and vanadium oxide.
 3. The method ofplating a nonconductor product according to claim 1, wherein thesemiconducting powder has a particle diameter in the range from 0.1 to1,000 μm.
 4. The method of plating a nonconductor product according toclaim 1, wherein the solution suspending the semiconducting powder is anaqueous or nonaqueous solution.
 5. The method of plating a nonconductorproduct according to claim 1, wherein the irradiated light isultraviolet light or visible light.
 6. The method of plating anonconductor product according to claim 1, wherein the polar group isformed directly on the surface of the nonconductor product.
 7. Themethod of plating a nonconductor product according to claim 1, whereinthe nonconductor product is formed with material selected from the groupconsisting of resin, rubber, ceramic and glass.
 8. The method of platinga nonconductor product according to claim 1, wherein the nonconductorproduct comprises a resin containing semiconducting powder.
 9. Themethod of plating a nonconductor product according to claim 1, whereinelectroplating with a different or the same kind of metal is furtherperformed on an electroless-plated layer formed by electroless plating.10. The method of plating a nonconductor product according to claim 1,wherein electroless plating with a different or the same kind of metalis further performed on an electroless-plated layer formed byelectroless plating.
 11. The method of plating a nonconductor productaccording to claim 9, wherein, in electroless plating, metal selectedfrom the group consisting of nickel, copper, gold, silver, and ametallic compound thereof is used.
 12. A method of plating anonconductor resin product, comprising the steps of soaking the resinproduct in water or a solution; bubbling air bubbles in the water orsolution while carrying out ultraviolet treatment of the resin productand electroless plating the resin product to form an electroless platinglayer thereon.
 13. The method of plating a nonconductor productaccording to claim 12, wherein the solution is a solution containing adissolved oxidizing agent or alkali material.
 14. The method of platinga nonconductor product according to claim 12, wherein, after theultraviolet treatment and before the electroless plating, a secondtreatment is performed in which the resin product is contacted with atleast one of an anionic surfactant and a nonionic surfactant as well asa solution containing an alkali ingredient(s).
 15. The method of platinga nonconductor product according to claim 12, wherein electroplatingwith a different or the same kind of metal is further performed on theelectroless-plated layer formed by electroless plating.
 16. The methodof plating a nonconductor product according to claim 12, wherein asecond step of electroless plating with a different or the same kind ofmetal is further performed on the electroless-plated layer formed by theelectroless plating.
 17. The method of plating a nonconductor productaccording to claim 15, wherein, in the electroless plating, a metalselected from the group consisting of nickel, copper, gold, silver, anda metallic compound thereof is used.